(1) Field of the Invention
This invention relates to a density measuring device for color plate-making. More particularly, the invention relates to a density measuring device for measuring the optical densities of color pictures or patterns to be printed, in which the original picture is scanned by a television camera and the resultant electrical signals are electronically processed and displayed on an oscilloscope so as to measure the maximum and minimum color densities of the original picture.
(2) Description of Prior Art
When graduated color image such as a color picture is printed, it is necessary to measure the optical densities of color components such as yellow (Y), magneta (M), cyan (C) and black (Bl) of the original picture, and especially, the optical densities in highlight and shadow portions must be accurately measured in order to determine the working conditions for the color separation in plate-making.
Even though the measurement of the optical density in a white highlight portion with the conventional densitometer is relatively easy, when the original picture has no white highlight portion, the setting of highlight level in plate-making is somewhat difficult. Further, when the maximum and minimum densities are measured according to the conventional method, it is necessary that several highlight and shadow portions in an original picture are checked up with the naked eye, all the densities of such portions are measured and the resultant values of densities are compared together so as to determine the maximum and minimum values. This procedure takes much labour and troubles.